Rear Tires Cupping?

91K miles on my ‘12 DCSB OR.
New tires ~8k miles ago, rotated ~2K miles ago. New Fox stage 4 suspension ~10K miles ago. Alignment done when I put the suspension on.
I had the normal whaaaaaaaaa sound from the tires like all aggressive tires but within the last ~1K miles there’s a new sound. It’s a cyclic/rhythmic wawawawa sound that increases with speed until it’s a solid hum.
Took my truck to Discount today and they said the rear tires are cupping. I had them swap front to rear on only the right side and the wawawawa sound decreased by ~50%. Just went back and had them swap the left side front to back but haven’t driven it. I drove across the parking lot to the alignment shop to have them check that and they’ll compare it to the last time I was here.
How do tires cup on the rear with a solid axle and new suspension components?
Could they’ve started cupping when they were on the front and just continued that process after being put on rear and it’s just recently gotten bad enough to notice it?

 

Cupping is usually bad or weak shocks/suspension, letting the tire contact the ground differently (and wearing differently).

You can have that issue regardless of axle type.

 

I've seen under inflated tires cup on front and rear.

 

It’s all new so I can’t see that being the issue. Thanks.

 

38psi front
36psi rear as I always have no load

 

That’s a hell of a trade-off that I’d be willing to make!!!!!!

 

Just one factor of cupping, not necessarily the source.

Something is causing it, and it’s suspension or tire pressure. It doesn’t just happen.

 

On any event, have you checked with the tire shop? You might be able to have those replaced under manufacturer warranty (defect).

America’s Tire/Discount Tire is really good about that, if you bought from them.

 

Yes. Discount, where I bought them, just said it’s something wrong with the rear of the truck. So far, the alignment shop is saying it’s the tires.

 

Could always speak to manager and have some written word from alignment shop.

AT/DT did that for me with 4 different tires, I never asked for it or pushed it either. I never had cupping issues so maybe that’s a different flow.. but for repeated vibes despite endless amounts of balancing and rebalancing, they condemned 4 and gave me new ones. First set had 12k miles on them.

 

Alignment/mechanic shop thinks it the low pressure in the E rated tires. They’ll hold 80 but DT put 34 in them. He said try it at 50 and see what happens. He thinks it went away by putting them on the front because the weight of the engine. I have no spare mounted and no weight in bed.

 

I got these tires because DT warranties/replaced the Cooper STT Pros I had originally bought (4K miles) were junk.

 

36 pounds with no spare or any weight in/ on the bed should be plenty. I run 38-40 in mine with around 500 pounds in/ on the bed.

 

To recap:
Tires rotated front to back/back to front.
Alignment specs are perfect for my lift.
Tires were at 34psi now they’re 50psi.
The sound has lessened. It has also changed in pitch and speed. I’ll give this a couple 1,000 miles to see if the psi changes things then update this.
Thanks!

 

pretty much every aggressive tire with vastly different sized lugs wears wacky.

 

50PSI??!

 

Ask the alignment shop to check the thrust angle of the rear axle. Have someone drive your truck while you follow behind, see if it tracks sideways down the road.

 

That’s some funny shit right there!!!

 

They're load range E so the max is 80psi.